This invention relates to a method and apparatus for forming a toner image by developing a latent electrostatic image with a dry developing agent in electrophotography and electrostatic recording.
In electrophotography and electrostatic recording, a latent electric image comprising a charge pattern or a conductivity pattern is formed on or in a photoconductive photoreceptor or a dielectric insulator (which are hereinafter collectively referred to as "a recording medium") and subsequently rendered visible by development through deposition of pigmented particles (toner). To implement these image forming methods, many techniques and apparatus have been proposed. Japanese Patent Publication Nos. 55708/1988 and 47392/1980 disclose a laser printer that combines electrophotographic technology with laser beam scanning technology and its use is gaining in popularity because of the ability to print out computer information. However, the demand for recording images of finer and higher-quality with higher process reliability using a smaller apparatus is ever increasing today and cannot be fully met by the conventional methods and apparatus for forming a toner image. From the viewpoints of ease of handling and of image quality, a latent electric image is conventionally rendered visible by methods of development that use a dry toner powder (see Japanese Patent Publication Nos. 30946/1985, 10869/1979 and 25356/1988) but considerable difficulty has been encountered in producing finer images of higher quality with the conventional dry developers agents and the image forming apparatus that use them.